What does Donald Trump need to do to nail down the Republican nomination?

The last thing one would expect. Money.

The last remaining, major piece in the Trump campaign is a successful, powerful, independent super political action committee to answer the bombardment which is only beginning. And that requires money.

No matter how rich Mr. Trump may be, no one has the liquidity to toss another $1 billion into the fight. Only a PAC, supported by Trump's best friends and masses of supporters can raise the money to close the deal for the nomination and keep him in the running in a general election fight that promises all of the attrition and violence of the Russo-German front during World War II.

But why a PAC? Why not his own presidential campaign? Because a donor cannot give more than $2,700 each to his campaign and the ways around it are mined with legal issues.

But a donor can give as much as he or she wants to a PAC. And it will take big money to force the anti-Trump GOP establishment to back down and to beat Hillary Clinton.

What will a PAC do for him?

1. It will help organize his ground game and get Trump loyal delegates to the RNC. This requires identifying Trump supporters and turning them out to the remaining district and state conventions where they can contest for delegate spots to Cleveland.

If this doesn't happen soon, Cruz will continue to put his people in place as he has done in Georgia and Louisiana and is in the process of doing in Arizona. At best, one could see a convention that cheers more for Cruz than Trump.

At worst Trump could have the nomination taken away.

Even minimal work by a Trump PAC could defeat that. But the clock is ticking. Many state conventions are already over.

2. It would end the stop Trump cottage industry.

The stop Trump movement has become the industry of choice for all of the out of work political operatives from the other 16 presidential campaign.

And it is beginning to pose a very serious problem.

While its negative advertisements and mischief at district and state conventions were at first only seen as irritants to getting the nomination, they are beginning to move numbers among Independents, women and other groups that Trump will need in the general election.

For most of the anti-Trump operatives it is not about stopping the candidate it is about paying the mortgage. They gambled on their own candidates and lost. No hard feelings.

Now they are making a living working for GOP establishment folk who favor an "open" convention or want to bring Trump to heel and get promises of corporate welfare and the right people in the right places. But the more they work the more invested they become.

And the closer to the general election we get the more money starts flowing to them from Democratic donors and special interests who favor Hillary Clinton.

If a Trump super PAC starts answering ad for ad, pundit for pundit, calling for unity and exposing their funding, the stop Trump operatives will evaporate like snow on a hot afternoon.

Once again. It is a problem that can be fixed now but too little, too late could spell doom.

3. It will put in place the massive machinery needed to win a general election contest against Hillary Clinton.

Some things take time. No matter how much money you have or how fast you are working. Donald Trump the builder of hotels knows that very well.

And there are things that a PAC should be doing now to make a difference in November.

4. A PAC can say and do things that the candidate should not say or do.

At some point, Donald Trump must appear presidential and let his PAC become his mad dog. That is its traditional role. But it won't work if its not seen. And it won't be seen if it's not on television.

And it won't be on television if it doesn't get funding fast.

Finally, there is this. A PAC offers a donor their best chance to seal their friendship with a future president. Trump decries such arrangements but when the dust settles and Trump takes a survey of who helped him the most he will not miss the large donations that came to the PAC that put him in office.

Most Trump super PACs have received cease and desist letters from the Trump campaign.

The Great America PAC, launched by Eric Beach is an exception and is running full board.

It bears watching.

Lots of people are calling for a ban on PACs and resent their influence in presidential campaigns.

In the meantime, Trump better get one going or he will be watching the inauguration of Hillary Clinton from the presidential suite of one of his hotels.
Doug Wead is a presidential historian who served as a senior adviser to the Ron Paul presidential campaign. He is a New York Times best-selling author, philanthropist, and adviser to two presidents, including President George H.W. Bush, with whom he co-authored the book "Man of Integrity." Read more reports from Doug Wead — Click Here Now.

A PAC offers a donor their best chance to seal their friendship with a future president. Trump decries such arrangements but when the dust settles and Trump takes a survey of who helped him the most he will not miss the large donations that came to the PAC that put him in office.